Influence of Alloying Elements on the Kinetics of Austenite Transformation in Powder Steels

Structural materials obtained by powder metallurgy methods are the most common type of such products, widely used in mechanical engineering and instrument making. This paper investigates the features of the formation of the structure and properties of alloyed powder steels. The study analyzes the influence of the method of introducing alloying components (carbide-forming elements Cr, Mo, W), their dispersity, as well as sintering parameters on the homogenization of the material. It is shown that complete dissolution of alloying elements, especially large particles, requires high temperatures (up to 1300°C) and long isothermal holdings. Particular attention is paid to the effect of porosity on the kinetics of austenite transformation. It has been established that an increase in porosity reduces the incubation period and increases the temperature of the onset of the martensitic transformation (Mn point). The influence of chromium and molybdenum on the critical points Ac1 and Ac3, as well as on the hardness after quenching, is analyzed. It is shown that in complex-alloyed powder steels, due to chemical heterogeneity, insoluble carbides may form, reducing the hardness of the material.